Given a number N, the task is to find the Nth term of the following series.
-2, 4, -6, 8……
Examples:
Input: n=4 Output: 8 Input: n=3 Output: -6
Approach: By clearly examining the series we can find the Tn term for the series and with the help of tn we can find the desired result.
Tn=-2 + 4 -6 +8 …..
We can see that here odd terms are negative and even terms are positive
Tn=2(-1)nn
Tn=(-1)n2n
Below is the implementation of above approach.
CPP
// C++ implementation of the approach #include <bits/stdc++.h> using namespace std;
// Function to return the // nth term of the given series long Nthterm( int n)
{ // nth term
int Tn = pow (-1, n) * 2 * n;
return Tn;
} // Driver code int main()
{ int n = 3;
cout << Nthterm(n);
return 0;
} |
Python
# Python3 implementation of the approach # Function to return the nth term of the given series def Nthterm(n):
# nth term
Tn = (( - 1 ) * * n) * ( 2 * n)
return Tn;
# Driver code n = 3
print (Nthterm(n))
|
Java
// Java implementation of the approach import java.util.*;
import java.lang.*;
import java.io.*;
public class GFG {
// Function to return the nth term of the given series
static int NthTerm( int n)
{
int Tn
= (( int )Math.pow(- 1 , n)) * 2 * n;
return Tn;
}
// Driver code
public static void main(String[] args)
{
int n = 3 ;
System.out.println(NthTerm(n));
}
} |
C#
// C# implementation of the approach using System;
public class GFG {
// Function to return the nth term of the given series
static int NthTerm( int n)
{
int Tn
= (( int )Math.Pow(-1, n) * 2 * n);
return Tn;
}
// Driver code
public static void Main()
{
int n = 3;
Console.WriteLine(NthTerm(n));
}
} |
PHP
<?php // PHP implementation of the approach // Function to return the nth term of the given series function Nthterm( $n )
{ $Tn = (pow(-1, $n )) * (2*n);
// nth term of the given series
return $Tn ;
} // Driver code $n = 3;
echo Nthterm( $n );
?> |
Javascript
<script> // JavaScript implementation of the approach // Function to return the // nth term of the given series function Nthterm( n)
{ // nth term
let Tn = Math.pow(-1, n) * 2 * n;
return Tn;
} // Driver Function // get the value of N
let N = 3;
// Calculate and print the Nth term
document.write( Nthterm(N));
// This code is contributed by todaysgaurav </script> |
Output:
-6
Time Complexity: O(log n)
Auxiliary Space: O(1)